When you change exhaust systems, you need to keep the servo motor from the original exhaust, plugged in to the harness. If it's just dissconnected the computer will sense it, and set the FI light. You can remove the servo motor from the original system, plug it in, and zip tie it out of the way. There are also devices to plug in, that will simulate the servo motor's load, to keep from setting the error light. Those work fine also.